1. Field of the Invention
This invention relates to a magnetoresistive effective element, a thin film magnetic head, a magnetic head device and a magnetic recording/reproducing device.
2. Related Art Statement
A magnetoresistive effective element (hereinafter, called as an “MR element”) has been employed in a magnetic storage element, a magnetic sensor or a thin film magnetic head. As of now, the MR element is made mainly of a giant magnetoresistive effective film such as a spin valve film (hereinafter, called as an “SV film”) or a ferromagnetic tunnel junction film (hereinafter, called as a “TMR film”). Among the exemplified MR elements made of the giant magneto-resistive effective films, an attention is paid to the MR element made of the TMR element film as a component of an M-RAM (magnetic random access memory).
In contrast, a composite type thin film magnetic head, where a reproducing head and a recording head with an inductive type electromagnetic conversion element are stacked, has been widely available as the thin film magnetic head. With the thin film magnetic head, the GMR element is utilized as the reproducing head, and vast researches and developments are made to the reproducing head with the recently rapid development in high density recording of a hard disk (HDD).
It is required for the reproducing head to reduce the Barkhausen noise therein. In order to reduce the Barkhausen noise, for example, a biasing magnetic field is applied to the MR element in the long direction thereof by means of a permanent magnet or a biasing magnetic field applying layer (magnetic domain controlling layer) made of a ferromagnetic layer and an antiferromagnetic layer which is provided at both sides of the MR element.
With the biasing magnetic field applying layer, the biasing magnetic field applying layer and the electrode layer are thicker than the SV portion of the MR element, so that in the thin film magnetic head with the MR element, the top shielding film is deformed convexly toward the MR element. In this case, the recorded magnetic field from a recording medium is absorbed by the sides of the MR element, so that the recorded magnetic field is transmitted to the high sensitivity region at the center track of the recording medium to widen the effective track width thereof. In this point of view, it is proposed in Patent publication No. 1 to form a soft magnetic film partially on the electrode layer to reduce the reading bleeding of the track edge of the recording medium.
With the above-mentioned structure proposed in patent publication No. 1, however, the magnetic domain structure of the edges of the soft magnetic layer becomes complicated, so that the magnetic field from the edges of the soft magnetic layer affects on the MR element to generate a side lobe defect therein.
In contrast, it is proposed in Patent publication No. 2 to set the gap distance (G1s) of the electrode portion relatively larger than the gap distance (G1c) of the SV portion to reduce the effective track width.
In order to reduce the effective track width sufficiently, however, it is found, it is required to satisfy the relation of G1s<G1c. In this case, the biasing magnetic field applying layer and the electrode layer are required to be formed much thinner, so that the output of the MR element is fluctuated due to the Barkhausen noise, which is originated from the thinner biasing magnetic field applying layer and the head noise is increased due to the increase in resistance of the thin film magnetic head, which is originated from the thinner electrode layer.                Patent Publication No. 1:        Japanese Patent Application Laid-open No. 11-175928        Patent Publication No. 2:        Japanese Patent Application Laid-open No. 2002-280643        Patent Publication No. 3:        Japanese Patent Application Laid-open No. 11-25431        